1. Field of the Invention
The present invention relates to an apparatus for the chemical treatment of disc-shaped semiconductor and silicon substrates, such as wafers.
2. Description of the Prior Art
Apparatus of this type is used for the purification before further treatment and for the chemical or physical treatment of such substrates, particularly wafers. The treatment may be automated to a large extent, and it is also known to automate the removal of the wafers from storage containers, the feeding of the wafers to the treatment chamber and the removal therefrom. In the most common wet-treatment, a multiplicity of wafers is brought into a bath in a common carrier. The dwell time of the carrier in the bath determines the progress of the treatment, for instance the etching. Different treatments, for example, etching, flushing and subsequently renewed etching, or coating require placing the carrier with the wafers in different baths. If only one surface of the wafer is to be treated, which is frequently the case, the opposite side must be protected from the treatment fluid, for example by applying a protective lacquer, which has to be subsequently removed.
Because of the difficulties encountered and also because, despite the circulation of the treatment medium or movement of the carrier in the bath, different treatment results have been obtained even with identical wafers, it is preferred to treat the wafers singly in an apparatus which comprises a treatment chamber with a carrier holding the wafer and nozzles applying fluids to at least one surface of the wafer. Apparatus of this type is known from Austrian patent No. 389,959 and Austrian utility model No. 000 639. A rotatingly driven substrate carrier is used, and stationary nozzles apply the treatment fluid thereto, the rotation having the object of distributing the fluid uniformly over the surface of the substrate. The chemical reaction is defined by the dwell time of the wafer in the treatment chamber, the rotary speed and the amount of the applied fluid. If only one surface is to be treated, the opposite surface of the wafer must be protected. In the known apparatus, the substrate carrier defines an annular wedge-shaped gap tapering outwardly from the center and ending at the edge of the substrate, and a protective gas is applied thereto under superatmospheric pressure. Using the so-called Bernoulli-effect, the flow of the treatment fluid due to the rapid rotation of the substrate carrier causes a vacuum at the edge of the substrate so that the protective gas is sucked off from the edge. To make it possible to use different treatment fluids, the substrate carrier may be vertically adjustable in a correspondingly high treatment chamber, and the fluid applying nozzles may be mounted vertically spaced in the chamber wall.
The known apparatus is complex and has a relatively large treatment chamber volume so that different treatment temperatures must be adjusted primarily by correspondingly controlling the temperature of the treatment fluids. Most importantly, the known apparatus has the disadvantage that different flow velocities of the treatment fluids over the substrate surface are generated by the rotation of the substrate and the application of the fluids by stationary nozzles so that the chemical reactions proceed differently over the substrate surface. Furthermore, it is almost impossible to treat the substrates fully with different fluids. Therefore, the wafers are usually treated in different chambers for different treatments. It is very difficult to use toxic and strongly etching media in the known apparatus.
It may be mentioned that it is known from U.S. Pat. No. 5,489,337 to lacquer wafers with a discharge nozzle for the lacquer, which extends over the diameter of the wafer and has a discharge slit. The opening width of the discharge slit is adjustable in accordance with the wafer width as the nozzle passes over the wafer. Such lacquer coating apparatus differs fundamentally from the type of chemical treatment apparatus with which this invention deals.
It is a primary object of the invention to provide an apparatus of the first-described type which not only has a simply constructed treatment chamber and substrate carrier but also enables the disc-shaped semiconductor or silicon substrate to be treated rapidly and uniformly, as well as to permit the substrate to be subjected to various treatments including final drying, to use toxic and highly corrosive treatment media without endangering the environment and the operating personnel, and even, if desired, to treat only one surface of the substrate while protecting the opposite surface without causing problems.
The above and other objects are accomplished according to the present invention with an apparatus for the chemical treatment of disc-shaped semiconductor substrates, such as wafers, which comprises a fluid-tight treatment chamber, a carrier for holding at least one disc-shaped substrate in the chamber, and an elongated spraying head having a plurality of nozzles for applying a fluid to at least one surface of the substrate. The spraying head is adjustably mounted in the treatment chamber and has a length corresponding at least to the diameter of the disc-shaped substrate. Fluid inlet conduit means have portions leading from outside the treatment chamber into the chamber to the nozzles, the fluid inlet conduit means portions in the chamber being adjustable with the spraying head. Adjustment drive means are provided for displacing the spraying head transversely relative to the substrate over the surface thereof whereby the nozzles sweep over the surface in substantially parallel tracks, and at least one outlet is connected to a suction device for removing the applied fluid from the treatment chamber.
In this apparatus, the treatment fluids, whether liquid or gaseous, may be applied to the substrate surface(s) substantially more uniformly and with greater flow velocity while a uniform flow velocity of the fluid may be maintained in all areas. Thus, a more uniform treatment result, for example in etching, may be obtained than with apparatus featuring rotating substrate carriers. Each treatment step is shortened because of the increased fluid flow velocity and the possibility of distributing larger amounts of treatment fluid over the surface(s) in the same time period.
The apparatus may further comprise fluid flow shut-off members in the fluid inlet conduit means outside the treatment chamber for selectively opening and closing fluid flow to at least some of the nozzles and to connect the nozzles to different inlet conduits. This makes it possible to shut off the fluid flow to selected nozzles or to connect such nozzles to different inlet conduits to enable the treatment to be matched to the surface area of the substrate being swept by the nozzles. The spraying heads may have different types of nozzles exchangeably mounted in the treatment chamber, together with different inlet conduit means for different fluids. The fluid inlet conduit means portions in the chamber may comprise different inlet conduits. In this way, different treatment media may be applied simultaneously or in succession. For example, different chemical substances for etching are fed to the nozzles in succession, each chemical substance being sucked off after each treatment and the complete removal of the chemical substances from the surface(s) not being spun off as heretofore but being flushed off by distilled water or another suitable liquid and subsequent drying, preferably with an inert gas, such as nitrogen, or spraying with alcohol, with subsequent partial evacuation of the treatment chamber. The treatment fluids may be aspirated from the chamber and re-used at least to a large extent. Since the chamber is hermetically closed, highly concentrated, aggressive or toxic chemicals may be used for the treatment of the substrates because the chemicals are sucked off, and the treatment chamber may be flushed several times or even dried before it is opened.
The apparatus may comprise a guide rod carrying the spraying head, the elongated spraying head extending transversely to the guide rod, the guide rod being adjustably movable in its longitudinal direction and the portion of the guide rod outside the treatment chamber being connected to the adjustment drive means. Preferably, the guide rod is hollow and forms at least a portion of the fluid inlet conduit means, and the hollow guide rod may pass out of the treatment chamber through a sluice chamber flushed with an inert medium.
It may be useful for the treatment of different wafers or the wafer treatment in a number of steps to mount two or more spraying heads having different types of nozzles, such as spraying, flushing and blowing nozzles, exchangeably in the treatment chamber, together with different inlet conduit means for different fluids.
If desired, the treatment chamber may have windows through which the treatment in the chamber may be observed, and/or measuring instrumentation for measuring the progress of the treatment.
The treatment chamber of the apparatus of this invention may have a relatively small volume and may be much less massive than treatment chambers of known apparatus of this type.
Therefore, it is possible and useful to arrange temperature regulating means outside the treatment chamber for heating or cooling the chamber. In this way, the required treatment temperatures may be generated and maintained at a constant level in the chamber.
If required, the apparatus may be so constructed that both surfaces of the substrate may be treated. In this case, the spraying head may be stationary and the substrate carrier may be reciprocable.